An antibody may be directed against one or more different antigens or one or more different epitopes on the same antigen. For example, a bispecific antibody is directed against two different antigens or two different epitopes on the same antigen. As bispecific antibodies can simultaneously bind to two distinct targets, these antibodies have great potential for antibody-based diagnosis and for the treatment of various diseases and disorders such as cancer, infectious diseases, autoimmune diseases, and blood diseases. For example, bispecific antibodies can selectively stimulate and expand T lymphocytes (Wong, et al., J. Immunol. 139:1369-1374, 1987; Wong, et al., Clin. Immunol. Immunopathol. 58:236-250, 1991), direct immune cells or toxic agents to kill tumor cells (Lum, et al., Exp. Hematol. 34:1-6, 2006; Wolf, et al., Drug Discov. Today 10:1237-1244, 2005; Cao, et al., Adv. Drug Deliv. Rev. 55:171-197, 2003; Talac, et al., J. Biol. Regul. Homeost. Agents 14:175-181, 2000), and simultaneously block two receptors (Lu, et al., J. Biol. Chem. 279:2856-2565, 2004). In addition, a bispecific antibody may be used as a substitute for Factor VIII to enhance enzymatic reaction (US Patent Application No. 2007/0041978) or to direct stem cells to the site of injury in patients with myocardial infarction (Lum, et al., Blood Cells Mol. Dis. 32:82-87, 2004).
Bispecific antibodies targeting tumor-associated antigens and toxic agents may be used in cancer therapy. For example, using this technology, one arm of the bispecific antibody may be directed to a tumor-associated antigen such as Her2, EGF receptor, CD20, CD22, CD30, CD33, CD52, and CA-125, and the other arm of the bispecific antibody may target a toxin, drug, or cytokine. That is, bispecific antibodies may selectively direct toxic agents to tumor cells enhancing the efficacy of therapeutic antibodies and decreasing systemic toxicity. Examples of toxin/drug include calicheamicin, doxorubicin, epirubicin, methotrexate, ricin A, saporin, gelonin, and vinca alkaloids, and cytokine examples include tumor necrosis factor alpha (TNF-alpha) and IL-2.
Specific cleavage by proteases of defined sites in biologically important effector proteins is a well known method for the natural control of cellular and extracellular physiological processes. Examples include protease activation and inhibition of the coagulation cascade (Butenas, et al., Biochemistry 67:3-12, 2002; Esmon, Chest, 124:26S-32S, 2003), protease activation of protease-activatable receptors (Coughlin, Arterioscler. Thromb. Vasc. Biol. 18:514-518, 1998), protease release of membrane associated cytokines (Amour, et al., FEBS Lett. 435:39-44, 1998), protease processing of prohormones in secretory vesicles (Moore, et al., Arch. Physiol. Biochem. 110:16-25, 2002), and protease processing of proproteins during secretion (Scamuffa, et al., FASEB J. 20:1954-1963, 2006). Proteases are often expressed or located in a tissue-specific or tumor-specific manner and examples include the membrane serine protease corin in heart tissue (Yan, et al., Proc. Natl. Acad. Sci. USA 97:8525-8529, 2000), the kallikrein serine protease prostate-specific antigen (PSA) in prostate tissue, prostate cancer, and seminal fluid (Veveris-Lowe, et al., Semin. Thromb. Hemost. 33:87-99, 2007), the membrane serine protease hepsin in liver tissue and tumors (Xuan, et al., Cancer Res. 66:3611-3619, 2006), coagulation protease factor X expressed in the liver and secreted into blood (Miao, et al., J. Biol. Chem. 267:7395-7401, 1992), and digestive proteases expressed in the pancreas and released to the duodenum (Belorgey, et al., Biochem. J. 313:555-560, 1996). Specific cleavage of amino acid sequences by human proteases include thrombin (Chang, Eur. J. Biochem. 151:217-224, 1985), factor Xa (Nagai, et al., Methods Enzymol. 153:461-481, 1987), furin (Brennan, et al., FEBS Lett. 347:80-84, 1994), subtilisin-like prohormone convertases (Lipkind, et al., J. Biol. Chem. 270:13277-13284, 1995), and the matrix metalloproteinases (Minod, et al., J. Biol. Chem. 281:38302-38313, 2006). Genes encoding specific proteases may be up-regulated in tumor tissue and Table 2 indicates proteases that are associated with cancer tissue.
Protease cleavage is widely used in in vitro studies to specifically remove protein or peptide tags from recombinant proteins or to process hybrid recombinant proteins. For example, human rhinovirus 3C protease, thrombin, or factor Xa have been used to remove glutathione S-transferase (GST) tags (Dian, et al., Life Sciences News—Amersham Biosciences 10:1-5, 2002) and factor Xa has been use to process hybrid proteins (Nagai, et al., 1987). Proteases are often targets for drugs as a means to regulate biological processes; and examples include factor Xa (Phillips, et al., J. Med. Chem. 41:3557-3562, 1998), thrombin (Riester, et al., Proc. Natl. Acad. Sci. USA 102:8597-8602, 2005), urokinase (Killeen, et al., Br. J. Cancer 96:262-268, 2007), and factor VIIa (Kohrt, et al., Bioorg. Med. Chem. Lett. 15:4752-4756, 2005). Finally, proteins developed as biological drugs may be modified to prevent cleavage by proteases and to improve their stability in vitro or in vivo (Light, et al., Eur. J. Biochem. 262:522-533, 1999; Saenko, et al., Haemophilia 12:42-51, 2006).
Specific protease cleavage sites have been incorporated into linkers that link a toxin molecule to a targeting antibody in order to allow protease specific release of the toxin by intracellular proteases (Trail, et al., Cancer Immunol. Immunother. 52:328-337, 2003). Furthermore, targeting antibodies have been created in many formats. For example, bispecific antibodies have been developed to allow binding to two different antigens or two different epitopes of an antigen by a single antibody molecule (Segal, et al., Curr. Opin. Immunol. 11:558-562, 1999; Tomlinson, et al., Methods Enzymol. 326:461-479, 2000; Wu, et al., Nat Biotechnol. 25:1290-1297, 2007). Other bispecific molecules have been generated with the ability to block two receptors (Lu, et al., J. Biol. Chem. 279:2856-2865, 2004) and to recruit immune cells to attack cancer cells and tumor tissue (Loffler, et al., Leukemia 17:900-909, 2003; Lum, et al., Exp. Hematol. 34:1-6, 2006).
The present invention relates to a novel antibody format, for example, monospecific and multispecific antibodies. The antibodies of the present invention may be constructed by tandem linking of two different heavy chain (H) variable region domains (VH) and two different light chain (L) variable region domains (VL). The heavy chain and light chain may form a Fab-like or IgG-like molecule through the disulfide bond between constant (C) regions. Multispecific antibodies may be generated by linking more than two antibody variable domains.
The antibodies of the present invention may be modified by protease cleavage. These protease-regulated antibodies may be, for example, monospecific antibodies, bispecific antibodies, or antibodies with sequential binding-activity upon protease digestion in either, for example, Fab-like or IgG-like format. Protease control or regulation may be provided by a protease site located in, for example, a linker. These protease-regulated antibodies may be utilized for the diagnosis and treatment of various diseases, and provide an additional level of control for biological drugs for therapeutic or diagnostic applications.